Offline mode

Hello, Can you explain the best way to process offline mode for Demo application XData?

Currently this demo client generates exception: Class Name EWinHttpClientException", Message: Cound not perform WinHttp operation. Error: (12029) Could not connect to the server"

This is for both Push and Pull command in OnTimer events

That message simply means that the XData server is not available (cannot be reached). If that's the case, then of course you cannot replicate (sync) your data with the server, you will have to wait until the server is available. That's up to you how to handle such situations, you can simply catch the exception and ignore it.

Yes, I understand this. My question is about which is the best way to determine that I can send Push/Pull? In the main thread, this is freeze app, or I should create an additional thread to make Push/Pull and ignore exceptions? 

It's also up to you. That's the beauty (imho) of Echo: each step is separate of the workflow and independent of the others. You can call Push/Pull in a background thread, yes.